The Obama administration has stepped up its legal attack against Volkswagen, filing a lawsuit that accused the German automaker of violating US air-pollution laws with its scheme to install emissions-cheating software in its diesel engines.
The civil complaint filed by Justice Department officials in Detroit seeks unspecified damages stemming from the car company's use of "defeat devices" on more than 600,000 diesel engines sold in the United States under the Volkswagen, Audi and Porsche brands.
"Car manufacturers that fail to properly certify their cars and that defeat emission control systems breach the public trust, endanger public health and disadvantage competitors," said John Cruden, the attorney general for the department's Environment and Natural Resources.
"The United States will pursue all appropriate remedies against Volkswagen to redress the violations of our nation's clean air laws alleged in the complaint."
The suit is the latest legal salvo against Volkswagen, which acknowledged in September that some of its light-duty diesel vehicles had been equipped with software that thwarted emissions-controls tests. The software allowed the engines to burn more cleanly when the vehicles' computer detected that an emissions test was underway.
The lawsuit alleges that the defeat devices allowed Volkswagen models to emit far higher levels of nitrogen oxide than the law allows, violating the Clean Air Act and resulting in "harmful air pollution" in the United States.
The emissions scandal, which prompted the resignation of chief executive Martin Winkerhorn last fall, was initially limited to 2.0-litre diesel engines. Subsequent investigations expanded the list of affected vehicles to more than 11 million worldwide, including a number of 3.0-engine models.
The Environmental Protection Agency, which filed the initial notice of violation against Volkswagen in September, said the additional action was warranted because the car company still had not responded adequately to fix the problem.
"So far, recall discussions with the company have not produced an acceptable way forward," said EPA assistant administrator Cynthia Gyles, of the agency's Enforcement and Compliance Assurance office.
"These discussions will continue in parallel with the federal court action."
There was no immediate response to the lawsuit from Volkswagen. Company officials have acknowledged that "misconduct" occurred, and have earmarked more than US$7 billion for making repairs to affected automobiles.